The men entered Collections Fine Jewellery, opposite South Yarra train station in Toorak Road, just after 3pm.

An unknown weapon was used to smash several cabinets, Victoria Police spokesman Luke Zammit said.

A male staff member suffered a cut to a hand. No one else was injured.

Police said the men fled in a stolen vehicle.

Lucinda Jenkins, who works at a nearby business, said she heard glass smashing and then saw three men run to a getaway car.

"[I saw] three males, of average height, with black material wrapped around their heads ... and there was a driver," she said.

"It was a black, small sort of vehicle, four doors. If I had to guess, it looked kind of like a Golf.

"There were people everywhere.

"I think it was just shock, really. Nobody really knew what to do.

"They just pulled up on the side of the road and I guess that caused a bit of a jam.

"I heard the smashing, but I think it would have only been like 30 seconds to a minute, max. It wasn't long."

It is not yet clear how much jewellery was stolen.

Collections is Australia's oldest horology dealership, restoring time-pieces and selling antique, estate and modern jewellery.

A spokesperson for the store declined to comment.

It is the second daylight robbery at a Melbourne jewellery store in as many days.

Three men used machetes and hammers to smash cabinets at Holloway Diamonds in Canterbury about 12.30pm on Friday.

The men fled in a blue Subaru station wagon, with registration 1IC 4SG, stolen from Truganina on Sunday.

A South Yarra jewellery store owner, Paul March, said all jewellers were nervous about the spate of robberies in Melbourne.

"Everyone would be reviewing their security, I would imagine," he said.

Anyone with information should call Crime Stoppers on 1800 333 000.